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~~ SCOTT, COX & ASSOCIATES, WC. uniudlin+~ on,gin,•i•o • ainrw~r. December 11, 2006 Hart Environmental P.O. Box 1303 Boulder, Colorado 80306 Attn: Mr. Michael Hart Project: 06605 Dear Mr. Hart: This report should be considered to be an addendum to our original report concerning the proposed Camenish Borrow Pit (to be located north of Weld County Road 20'~ and west of Weld County Road 7 in Weld County, Colorado). The original report is dated December 6, 2006. Since the preparation of that report we have reviewed the revised mining plan map, which includes a mining exclusion area for the gas well on the property and the conveyance piping that serves the well. Also, the new mining plan eliminates the stockpile areas, resulting in the offset of the proposed mined area to be within 200 feet of the adjacent Godding Ditch. Additionally, we understand that, although our report documents an angle of repose of approximately equal to a slope of 2:1, a shallower cut of 3:1 has been proposed for use at this site. In our original report we discussed the slope stability of the cut banks, based on the angle of repose of the site soils. Slumping of earth banks is wmmon, if the banks are cut steeper than the angle of repose (which is the angle that the soil will seek naturally, due to the frictional interactions of the soil particles). We have seen circular landslide analyses done, to accomplish this same thing. However, such failures are very rare in sand and gravel pits, where the banks have not been cut steeper than the natural angle of repose of the soil. Essentially, if the bank is cut to be no steeper than the angle of reppose, then soil stresses beyond the cut line are insignificant. Permit ~A'( d $ Confidental?: ~ Class: Pry„' MV# From: 'o s c~u &~o: /~ ~ Doc. Name: ocr cl..~-1 Doc. Date (if no date stamp): n ckR Section/Exh. Ni ';Sih tih,. ~l IS~n~IJ~~i, 1 . ~~n:~d~• 1{u InSpeCtlOn Date $peCIaIISt: ~ //~ ~~